Internet Protocol (IP) traffic can be routed across the Internet by using discovery and routing protocols that are executed by the nodes of the Internet such that they can determine optimal and loop-free routes from any data traffic source to any data traffic destination using topology information exchanged between the nodes. The process of arriving at these routes and forwarding tables can be called “convergence.” The routes and forwarding tables are recalculated when there is a change in network topology. However, re-calculating these routes and tables can take time (i.e., long convergence time) during which some traffic may be dropped or lost.
IP and Multi-Protocol Label Switching (MPLS) Fast Reroute (FRR) technologies address the problem with the long convergence of routing protocols by providing pre-calculated backup paths, which are used when network failures occur. These technologies are important due to the increased use of IP transport for real time services such as video, voice, television, and the increasing number of web services which are all expected to work without disruption.
The standard approach used in existing technologies, such as Open Shortest Path First (OSPF)/Intermediate System-Intermediate System (IS-IS)/Label Distribution Protocol (LDP) Loop-Free Alternate (LFA), Maximally Redundant Trees (MRT), and Border Gateway Protocol (BGP) Fast Reroute (FRR) is to gather network information using a routing/signaling protocol and based on that information compute the backup paths necessary to prepare for failures of adjacent links or nodes, and then to pre-provision the forwarding plane with those back-up paths. The forwarding plane is then able to react on a failure event and switch from a primary path to a back-up path without waiting for the routing protocol to gather updated network information and converge.